If your kitchen sink drain smells bad, the cause is usually trapped food, grease buildup, bacteria, a dry P-trap, or a drainage issue that is letting sewer gas into your home. This guide explains what different sink smells can mean, how to clean the drain safely, what not to pour down it, and when it is time to call a plumber.
What Does the Kitchen Sink Smell Tell You?
| Symptom | Likely cause | First step |
|---|---|---|
| Rotten-food smell | Food, grease or disposal buildup | Clean the strainer, stopper and disposal |
| Rotten-egg or sewer smell | Dry P-trap, vent problem or sewer gas | Run water and inspect the P-trap |
| Musty smell | Mold, moisture or a small leak | Inspect the cabinet and pipe connections |
| Smell only when water runs | Drain buildup, faucet aerator or water issue | Compare hot/cold water and other faucets |
| Several drains smell | Vent or sewer-system problem | Contact a plumber |
| Smell with slow drainage | Partial clog or organic buildup | Clean the trap or arrange drain cleaning |
7 Common Causes of a Smelly Kitchen Sink Drain
A smelly sink drain can dampen your kitchen’s aura and must be dealt with as soon as possible because it will only get worse. Here are several possible causes for the sink drain smells.
Food and Grease Buildup
Food, fat and grease can build up in your kitchen sink. They decompose and produce an unpleasant smell that makes your kitchen sink smell.
Bacteria and Drain Biofilm
Pipes and drainage systems provide the perfect environment for bacteria growth. As bacteria grows and spreads, the compounds formed can produce a terrible smell.
Dirty Garbage Disposal or Splash Guard
Food can get lodged in the drain and create a blockage. This may make the water stagnant, which accelerates the rotting process and produce an awful smell.
Dry or Leaking P-Trap
The P-trap holds a small amount of water that blocks sewer gases from coming back up through the drain. If it dries out, leaks, or is not sealing properly, the sink may start to smell like sewage or rotten eggs.
Partial Clog or Slow Drain
Food, grease, soap scum, hair, and other buildup can collect inside the drain and create a bad odor over time. If water drains slowly or the smell keeps returning after cleaning, there may be a partial clog deeper in the pipe.
Blocked Plumbing Vent or Improper Drain Slope
If your pipes were not installed properly with backpitched pipes, water may not flow freely through your plumbing system and cause food to get trapped.
Mold, Leaks or Water-Supply Odours
Moisture under the sink can lead to mold or mildew smells, especially if there is a small leak you have not noticed yet. In some cases, the odor may also come from the water supply itself, so it helps to check whether the smell is present in both hot and cold water.
How to Get Rid of Kitchen Sink Drain Smells
A foul smell from a kitchen sink is off putting and embarrassing if you have guests. Using scented candles and other fragrances to mask smelly kitchen sink drains do not address the issue. Instead, try some of these simple ways to remedy a smelly kitchen sink:
- Identify whether the smell comes from the drain, disposal, water or cabinet.
- Remove and clean the strainer or stopper. Sometimes the stopper is the culprit. Clean it thoroughly and remove all lingering food waste.
- Clean underneath the garbage-disposal splash guard. Deposit a few ice cubes into your disposal and add several teaspoons of salt. Turn the grinder on and allow the salt and ice to clean your grinders.
- Flush light grease buildup with hot water and dish soap. This is an effective solution and preventative measure. The boiling water will dissolve any food particles and bacteria or grease from the drain and wash it away.
- Use an enzyme-based drain treatment for organic buildup.
- Check whether the P-trap contains water.
- Remove and clean the P-trap only when the homeowner can do so safely.
- Check for leaks or moisture under the sink.
- Stop DIY treatment and call a plumber when the smell returns, several fixtures are affected, or sewer gas is suspected.
What Not to Put Down a Smelly Drain
When a drain smells bad, it can be tempting to pour in whatever seems strong enough to clear it. Some products and materials can make the problem worse, damage your plumbing, or create safety risks.
Do not mix chemical cleaners, bleach, vinegar, ammonia, or other household products in the drain. Certain combinations can release harmful fumes, and they may not fix the source of the smell. It is safer to use one appropriate cleaning method at a time and rinse the drain well.
Avoid pouring large amounts of grease, cooking oil, or fat down the sink. Grease may go in as a liquid, but it can cool, harden, and stick to the inside of the pipe. Over time, that buildup can trap food particles and make odors return.
When to Call a Plumber?
A smelly sink drain is not always a major plumbing problem, but some signs point to something deeper than a dirty drain:
- The smell returns within a day or two
- More than one drain smells
- The drain gurgles
- Water drains slowly or backs up
- The sink smells like sewage or rotten eggs
- There is moisture or mold under the sink
- The P-trap repeatedly dries out
- The smell appears when another appliance drains
- There is a suspected blocked vent
- DIY cleaning has not changed the smell
City Rooter provides professional drain and plumbing services for all your plumbing issues. Our services are reliable and include drains and sewers, water services, and plumbing. We are available 24/7 for plumbing emergencies. Get in touch today to put an end to stinky sink drains.